Anchoring means for abrasive disks



April 15, 1947. R, HOMEYER I 2,418,883

ANCHORING MEANS FOR ABRASIVE DISKS Filed April 6, 1945 IN VEN TOR.

{P0652 HOMYE Patented Apr. 15 1947 Niri-:o srr ANCHORING MEAN S FORABRASIVE DISKS Application April 6, 1945, Serial No. 586,929

This invention relates to the manufacture of abrasive articles. Moreparticularly it relates to bonded abrasive articles such as grindingwheels or discs of the type which are secured at the flat side surfaceof the article to a suitable mounting plate or frame for support and/orreinforcement during use. The invention is especially concerned with theanchoring means provided in such abrasive articles for mounting them ontheir supports; it also pertains to methods of making wheels or discs ofthe described type which, when warpage or distortionof the abrasive bodytakes place during the process of making, and especially during thefiring or curing of the article to its matured condition, will permitthe mounting face of the wheel to be facilely dressed to an acceptacleflatness within the tolerance necessary to provide a strong and firmattachment of the wheel or disc to its supporting plate or frame withthe anchoring means firmly and strongly retained in position.

According to the present invention, a bonded abrasive wheel or discadapted for mounting on a flat side face thereof is provided withanchoring means embedded in' the bonded abrasive body and substantiallyflush with the mounting face of the article. The anchoring meansconsists of a strong and tough metallic insert, such as a threaded steelnut, and a relatively thin washer of softer material, the latter beinglocated between the metal insert and mounting surface. The material ofthe washer is such that, if it is found necessary due to warpage duringfabrication to lap or otherwise dress the mounting surface of theabrasive article to provide a suitably fiat face for mounting, thewasher will be Worn down evenly with the surrounding bonded abrasivebody and will not become separated from the contacting abrasive body byvoids or cracks.

In order that the invention will be more clear- 1 1y understood and forillustrative purposes, reference is made to the accompanying drawings,in which: v

Figure 1 is a rear plan view of a grinding disc embodying the presentinvention, and showing the mounting plate partially broken away;

Figure 2 is a vertical cross-sectional view through the line 2-2 ofFigure 1;

Figure 3 is a vertical cross-sectional view through an anchoring meansof the type embodied in' the disc shown in Figures 1 and 2 together withthat portion or the abrasive body surrounding the anchoring means, anddepicts in exaggerated form the manner in which a part of the anchoringassembly during dressing is 4 Claims. (Cl. 51209) worn down even withthe surrounding bonded abrasive body to provide a flat external surface.

Referring further to the drawings, Figures 1 and 2 depict an abrasivegrinding disc adapted for side grinding and made in accordance with theteachings of the present invention. The abrasive disc illustrated inFigures 1 and 2 consists of an annular bonded abrasive body 4 having aflat side grinding face 5 and an opposite fiat supporting face ti. Thebonded abrasive body may be any desired dimension, the diameter of sucharticles differing over a wide range of sizes; wheels or discs of thedescribed type are usually several inches thick so as to provide anarticle of relatively long useful life. The bonded abrasive body 4 iscomposed of abrasive grain such as crystalline aluminum oxide, siliconcarbide, or other granular abrasive material of the desired grid size orsizes, suitably bonded. The bond may be a vitrified ceramic material, orit may be a silicate, or a resin, or a natural or synthetic rubbercompound.

As a support or means for mounting upon a grinding machine the abrasivebody 4 provided with a steel or other strong rigid backing plate 7attached to the flat face 6 of the abrasive body i by means of anchoringbolts Which are screwed into anchoring means 8. The backing plate I isprovided with a central arbor hole 9 and three bolt holes I?) forfastening the backed disc to a mounting plate on the grinding machine.(The corresponding mounting plate for the grinding machine is notshown.) Although the abrasive disc as shown in Figures 1 and 2 ispresented as attached to its mounting'plate, it is customary for thebonded abrasive body to be fabricated bythe manufacturer and supplied tothe user who attaches the mounting plate I at the time and place of use.The mounting plate 5 is attached to the bonded abrasive body by means ofanchor bolts I 3 which screw into and engage the threaded metal insertsII of the anchoring means 8. Alternatively a stud may be screwed intothe insert II and a nut placed on the outer end of the stud after thedisc has been put onto the supporting plate I.

A modified form of anchoring means wherein the metallic insert need notbe threaded may be employed in that type of reinforced abrasive Wheel ordisc in which the disc is secured to the backing plate by bolts insertedin the wheel through holes extending from the front grinding face of thewheel completely through the abrasive body and engaging a similarunthreaded anchoring insert and threading into the backing plate "w r ea.

itself. However, as in the case of the specific abrasive disc hereinillustrated, the metallic insert of the anchoring means is inset fromthe mounting face of the wheel and provided with a non-metalliccomposition washer or filling material between the metallic insert andthe mounting face. The anchoring means 8 are embedded in the bondedabrasive body 4 in such "position that the bottom side of the anchoringmeans lies flush with the mounting face 6 of the abrasive body. Thenumber of these anchoring means embedded in any particular wheel or discdepends largely upon the size of the wheel, but also upon the conditionsunder which the wheel is to be used such as the speed ofoperation,.severity of the grinding operation, etc. They are distributedover the mounting face of the wheel and are usually evenly spaced fromonelanother.

Each anchoring means consists of a strong, .tough,.threaded metal insertH, as, for example, a tapered steel nut, and-ha softer, more easily'abradablewasher i2. The metallic insert H is preferably tapered andpositioned with the large end of'the insert farthest away from themounting surface of thewheel or-disc soas to be more strongly gripped bythe surrounding abrasive "body. Instead of tapering the metal insert theouter'sides may beprovided with aseries of circumferential corrugationsor otherwise provided with an uneven contour at the sides to enhancethe-gripping action of the bonded abrasive body onthe insert. Thewasher4 2-is made of softer material than the'me'ta'l insert and is placedbetween the metal insert lliand-the mounting face fi of thewheelandfiushwith the latter. A composition washer-which has been found highlysatisfactoryfor the-purpose is a plain unthreaded Temper d Masonitewasher /8 thick. (Tempared Masonite is a-trade mark of theMasoniteCorp-oration for material consisting of processed woodfibers compressedby heatand pressure and bonded by the resinous content-toe strong, hardconditions) Qther materials can be used providedthat they stand-up underthe'temperatures employed "inmaturingthe bond of the abrasive bodyduring the making of thearticle, and have the property-of wearing-awayat a substantially equal rate with the surrounding abrasive body whenthe-two are subjected toalapping or comparabledressing operation.Materials which may be usedior washers include various organiccompositions such as various fibrou's materials, synthetic resins,natural andsynthetic hard rubbers, asbestos-cloth base phenolicmaterial, and the like. The kind of material used for the washer willdepend mostlyon the nature of thebond of the abrasive body.

In making an abrasive article of the herein describedtype, such as thatshown in Figures 1 and '2, the desired number of anchoring means,including composition washers and metal inserts are positionedinasuitable moldand the desired mixture of granular-abrasive and bondtherefore plaoed in the mold about-the anchoring means. If desired,thewashers may be cemented to the metal insert prior to positioning in:the mold assembly, asuitable cement for such purpose being a liquidphenoli'c condensation product resin thinned with a suitable solvent.Before introduction of JPthe abrasive mixture into the mold about theanchoring means, :the latter are ipreferably coated with a thinliquidlcement such as bond for the abrasive article and also anyauxiliary cementing or bonding means used in securing the anchoringmeans. In the case of organic bonds the bond may be partially orcompletely cured during the pressing operation although final cure isusually effected by an oven treatment at elevated temperatures followinthe removal of the'formed article from the mold.

Instead of using a preformed composition washer and molding it intoplace along with the metal insert simultaneously with the molding of thebonded abrasive body, a modified procedure, particularly adaptable tothe fabrication of ceramic bonded abrasive wheels and discs of thehereindescribed type requiring a high temperature firing to mature thebond, may be followed.

According thereto, the bonded abrasive body as molded and fired isprovided with reentrant portions or cavities adjacent the intendedmounting face and positioned the same as the anchoring means which areto be embedded therein but slightly larger in size than the latter.'Ihese holes or cavities may be provided by molding the abrasive bodyabout removable-inserts ofthetdesired size placed in the'mold prior tomolding or about inserts which are readily decomposable at thetemperature of firing. Such cavitiesmay also 'be provided by molding theabrasive body in solid form and drilling or otherwise forming thecavities while the bond i still in the unfired state. After the bondedbody has been matured, and before or after the mounting face has beendressed to a substantially flat condition, the metal inserts and washersare placed in position in the cavities and grouted in place by means ofa suitable cement such as a liquid reactive phenolic resin capable ofcold setting with acid hardener and usually mixed with some inertfiller. such as flint, fused quartz, air-floated asbestosetc. Ceramicbonded wheels or discs constructed by this method may have theinSerts-grouted with lead or a similar soft metal or-alloy-andthecomposition washers inserted and grouted in place with a suitableorganic cement as, for example, that given below. Grouting of theinserts in' this modified method for ceramic wheels is preferably thatsometimes used incemen'ting the washer -to the metal insert. The massis'then pressed to formed washers.

carried out with organic cements or alloys meltins; at a temperaturelower than the melting point for lead since grouting with molten leadtends to warp the abrasive body. However, after grouting of the insertsand washers in place the mounting face of the abrasive disc can again bedressed flat, if necessary.

When abrasive wheels or discs are provided with anchoring meansaccording to the above metal inserts from :being filled orsmeared withthe filling composition by temporary'rinsertion'of a plug which can beremoved afterfthe filler material has hardened. v

It is notunusual jforithe resulting abrasivetbiody tobe slightlywarpedor distortedduringthe-Jouring or firing operation. Such warpage'ishighly undesirable since a warpage as slight as two or threethousandths o'ian inch is suffi'ci'ent :to interfere with satisfactorymounting of the body on its supporting plate. The larger the wheel ordisc being made the more troublesome the warping or distortion problembecomes. In order to avoid the necessity of discarding warped wheels ofthis type efforts are made to lap or otherwise dress the mounting faceof the warped article to an acceptable degree of flatness for mounting.

Figure 3 is an exaggerated fragmentary view of an abrasive wheelstructure made in accordance with the present invention and embodyinganchoring means of the type herein described consisting of a toughinsert II and a washer l2 of softer material. The anchoring means inFigure 3 is shown after it has been submitted to a dressing or lappingprocedure to remove warpage of the article. The composition washer Ithas been worn down even with the surrounding abrasive body 4 so that themounting face 6a, including the external surface lila of the washer, isflat and free from any projecting portions. It is to be understood thatthe excessive tilt of the anchoring means as shown in Figure 3 is thuspictured for purposes of clarity and the actual warpage which takesplace is often up to A;, which however'must be removed if the article isto be rendered suitable for use.

As is clear from the above description, the present invention not onlyprovides an abrasive wheel adapted for mounting on a fiat side face butalso a method of reclaiming those wheels of the herein described typewhich become warped or distorted during processing, and which ifotherwise constructed would either have to be discarded or at leastrestricted to much lighter usage because of poor mounting ability orweakening of the anchoring assembly durin subsequent dressingoperations.

Having described the invention in detail it is desired to claim:

1. An abrasive article comprising a bonded abrasive body having agrinding surface and asubstantially fiat mounting face, said bondedabrasive body having embedded therein and substantially flush with saidmounting face a plurality of anchoring means, each of said anchoringmeans comprising a metallic insert and a nonmetallic washer, the latterbeing disposed between the metallic insert and the surface of saidmount- 6 ing face and substantially flush with the latter surface.

2. An abrasive article comprising a bonded abrasive body having agrinding surface and a substantially flat mounting face, said bondedabrasive body having embedded therein and substantially flush with saidmounting face a plurality of anchoring means, each of said anchoringmeans comprising a steel insert and a nonmetallic washer, the latterbeing disposed between the metallic insert and the surface of saidmounting face and substantially flush with the latter surface.

3. An abrasive article comprising a bonded abrasive body having agrinding surface and a substantially fiat mounting face, said bondedabrasive body having embedded therein and substantially fiush with saidmounting face a plurality of anchoring means, each of said anchoringmeans comprising a metallic insert embedded within said abrasive bodyand spaced inwardly of the abrasive body from the mounting surface ofsaid abrasive body, the intervening space between said metallic insertand the mounting face being filled with an organic compositionsubstantially as easily abradable as the surrounding abrasive body.

l. An abrasive article comprising a bonded abrasive body having agrinding surface and a substantially flat mounting face, said bondedabrasive body having embedded therein and substantially flush with saidmounting face a plurality of anchorin means. each of said anchoringmeans comprising a metallic insert embedded Within said abrasive bodyand spaced inwardly of the abrasive body from the mounting surface ofsaid abrasive body, the intervening space between said metallic insertand the mounting face being filled with a heat hardenable resinouscomposition.

ROGER H. HOMEYER. I

REFERENCES CITED UNITED STATES PATENTS Name Date Gardner May 9, 1922Number

